length of the hinder eight of the series of dorsal vertebræ. The extreme breadth of the distal end is 1⋅45 inch, the extreme breadth of the proximal end, from the inner surface of the articular head to the outer surface of the shaft, 1⋅73 inch. The femur is therefore slightly shorter in proportion to the length of the dorsal vertebræ than in Iguanodon. The faces of the inner trochanter look much more directly inwards and outwards, and the whole process has a different shape from that of Iguanodon. There is no pit above the inner trochanter, such as exists in Iguanodon; and the deep intercondyloid groove, on the anterior face of the distal end, which is so characteristic of Iguanodon, is wanting.
The remains of what I take to be the right fibula and tibia are seen in front of the pelvis. What remains of the fibula is 4 inches long, and shows the proximal end and moiety of the shaft tolerably entire. The former measures 0⋅7 inch from before backwards, but not more than 0⋅2 inch in width. The anterior edge of the shaft is turned towards the eye. An impression on the matrix is continued in the line of direction of the bone, and suggests that it was altogether about five inches long, and that its distal end had a width of 0⋅4 inch. In Iguanodon, the length of the tibia is to that of the femur as 31 to 33, and the fibula is somewhat shorter than the tibia. If Hypsilophodon followed the proportion of Iguanodon, the tibia should be 5⋅35 inches long, and the fibula rather more than five inches.
On reference to the memoir which I have cited, it will be observed that my interpretation of the bones described is very different from that adopted by Prof. Owen (p. 2). He terms the femur (65) "the right femur," and states that "the bones of the right hind leg are almost completed when the blocks containing their opposite ends are brought into juxtaposition." But the most cursory inspection is sufficient to show that the femur belongs to the left side, and, as I have proved, the so-called right tibia and fibula (66 and 67) are really the two ischia and the pubes.
I find myself compelled to dissent as widely from Prof. Owen's view of what he terms "the principal bones of the right hind foot." I have no sort of doubt it is the left hind foot. For there are two bones belonging to the distal tarsal series in their natural relation with one another, and with two, if not three, metatarsal bones. These bones are obviously the homologues of those which exist in Scelidosaurus and in the Crocodilia, and which lie on the outer side of the foot. The metatarsals which are connected with these bones, therefore, must needs belong to the outer, or fibular, digits; and, as the dorsal surface of the metatarsus is turned towards the eye, the foot can only be that of the left limb. In the proximal row of the tarsus lie a calcaneum (which seems to have a process as in Crocodiles) and an astragalus, with a convex distal face and seemingly flattened from above downwards. "Whether it has an ascending process cannot be distinctly made out. The proximal and the distal series of bones are dislocated, and what looks like the end of the tibia is seen between and below them. The metatarsals of the first, second, and
